Alemtuzumab induces caspase-independent cell death in human chronic lymphocytic leukemia cells through a lipid raft-dependent mechanism

Leukemia. 2006 Feb;20(2):272-9. doi: 10.1038/sj.leu.2404014.


Alemtuzumab is a humanized IgG1 kappa antibody directed against CD52, a glycosyl-phosphatidylinositol linked cell-membrane protein of unknown function. Herein, we demonstrate that alemtuzumab promotes rapid death of chronic lymphocytic leukemia (CLL) cells in vitro, in a complement and accessory cell free system. Using minimal detergent solubilization of CLL membranes, we found that CD52 colocalizes with ganglioside GM-1, a marker of membrane rafts. Fluorescence microscopy revealed that upon crosslinking CD52 with alemtuzumab+anti-Fc IgG, large patches, and in many cases caps, enriched in CD52 and GM-1 formed upon the CLL cell plasma membrane. Depletion of membrane cholesterol or inhibition of actin polymerization significantly diminished the formation of alemtuzumab-induced caps and reduced alemtuzumab-mediated CLL cell death. We compared alemtuzumab-induced direct cytotoxicity, effector cell-mediated toxicity and complement-mediated cytotoxicity of CLL cells to normal T cells. The direct cytotoxicity and observed capping was significantly greater for CLL cells as compared to normal T cells. Cell-mediated and complement-mediated cytotoxicity did not significantly differ between the two cell types. In summary, our data support the hypothesis that alemtuzumab can initiate CLL cell death by crosslinking CD52-enriched lipid rafts. Furthermore, the differential direct cytotoxic effect suggests that CD52 directed antibodies could possibly be engineered to more specifically target CLL cells.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural

MeSH terms

  • Actins / drug effects
  • Actins / metabolism
  • Alemtuzumab
  • Antibodies, Monoclonal / drug effects
  • Antibodies, Monoclonal / pharmacology*
  • Antibodies, Monoclonal, Humanized
  • Antibodies, Neoplasm / drug effects
  • Antibodies, Neoplasm / pharmacology*
  • Antigens, CD / biosynthesis
  • Antigens, CD / metabolism
  • Antigens, Neoplasm / biosynthesis
  • Antigens, Neoplasm / metabolism
  • CD52 Antigen
  • Caspases / drug effects*
  • Cell Death / drug effects
  • Cell Membrane / metabolism
  • Cytoskeleton / drug effects
  • Cytoskeleton / metabolism
  • G(M1) Ganglioside / biosynthesis
  • Glycoproteins / biosynthesis
  • Glycoproteins / metabolism
  • Humans
  • In Vitro Techniques
  • Leukemia, Lymphocytic, Chronic, B-Cell / drug therapy*
  • Leukemia, Lymphocytic, Chronic, B-Cell / pathology*
  • Membrane Microdomains / drug effects
  • Membrane Microdomains / metabolism*
  • beta-Cyclodextrins / pharmacology


  • Actins
  • Antibodies, Monoclonal
  • Antibodies, Monoclonal, Humanized
  • Antibodies, Neoplasm
  • Antigens, CD
  • Antigens, Neoplasm
  • CD52 Antigen
  • CD52 protein, human
  • Glycoproteins
  • beta-Cyclodextrins
  • methyl-beta-cyclodextrin
  • G(M1) Ganglioside
  • Alemtuzumab
  • Caspases